Method and device for filleting killed and headless fish, the abdominal cavity of which is opened up

ABSTRACT

Certain farmed and/or breeding fish such as tilapia are filleted after the fish have been beheaded, slaughtered and had their ventral cavity opened. Cuts are made in the dorsal region and on the ventral side in the caudal region for exposing the dorsal spokes and ventral spokes, respectively. Then, separating cuts are made over the vertebral column connecting the dorsal and ventral cuts. Before peeling separation in the region of the ventral cavity, the ventral lobes are trimmed by separation of the ends of their ventral lobe portions projecting beyond the ribs. Peeling separation is completed by peeling cuts adapted to the rib contour and made with at least two degrees of freedom.

[0001] The invention concerns a method for filleting fish which havebeen beheaded, slaughtered and had their ventral cavity opened, inparticular in the large-scale processing of breeding fish, especially ofthe species tilapia, wherein the fillets are detached from the bonestructure in the dorsal region by means of dorsal cuts which are made asfar as the vertebral column and expose the dorsal spokes/radialia and onthe ventral side on the one hand in the caudal region by means ofventral cuts which are made as far as the vertebral column and exposethe ventral or belly spokes/radialia as well as separating cuts whichare made over the vertebral column and connect the dorsal and ventralcuts and on the other hand by means of scraping or peeling separationwhich under laterally yielding counter-pressure is effected from thevertebral column along the ribs surrounding the ventral cavity. Further,the invention concerns a corresponding filleting apparatus, includingdorsal blades for exposing the dorsal spokes up to the vertebral column;ventral blades for exposing the ventral spokes in the caudal region upto the vertebral column; separating blades for separating the fillets inthe caudal region from the vertebral column, cutting through the ridgeleft by ventral and dorsal blades around the vertebral column, i.e. onboth sides thereof; a scraping tool including peeling blades and peelingblade supports for scraping/peeling separation of the fillets from theribs surrounding the ventral cavity under laterally yieldingcounterpressure from the vertebral column; an endless conveyor fortransport of the fish tail first and past the aforementioned toolsarranged on both sides of an imaginary conveying plane and also a numberof fish saddles arranged on the conveyor for reliably holding the fishin their ventral cavity for the purpose of transport and processing withthe tools.

[0002] A method and apparatus of this kind are basically known fromDE-A1 14 54 089. In the known apparatus, in addition to the ventralfilleting and dorsal filleting and separating blades for cutting theribs free which are basically known in the field of fish filleting,there is provided a scraping tool which with its cutting edge scrapesdirectly over the surface of the ribs or vertebral processes, so thatcompared with previously known rigid rib blades in this area no morefillet flesh remains on the bone structure and the yield can beimproved. When using such scraping tools, compared with apparatuses withrigid circular rib blades such as were used for decades before, it isnecessary to advance the separating cut for separating the strips offlesh left at the sides of the spine after the ventral and dorsalfilleting cuts, to before the rib cut, because the scraping bladelocated rigidly in the plane of the lower edges of the dorsal guidespushes the fillet off the ribs or vertebral processes as a result of itsplough-like action. But for this the fillet must be completely detachedin the caudal region.

[0003] However, with such a cutting sequence it turned out that, due tothe upsetting forces acting on the fillets in this region,irregularities arise in cut guiding and impair the filleting result inquality and yield. Furthermore it is not possible to ensure that theseparated fillets can always be discharged in a definite position, forexample lying flat on the skin side, which was and is a precondition forautomatic further processing without problems, e.g. skinning.

[0004] To remedy these drawbacks the apparatus known from DE-B 1 29 46042 was developed, in which the scraping tool is designed with ascraping blade arranged one on either side of ventral and dorsal guidesand beginning adjacent to the latter in a point, with cutting edgediverging in a wedge shape, and with a bead-like support which isallocated to the cutting edge and forms a gap with it and which alsostarts from a point adjacent to the ventral guide and laterally yieldsresiliently relative to the scraping blade. In this case the scrapingtool is vertically displaceable in such a way that shortly beforearrival of the ventral cavity end of the fish each scraping blade ismovable at least with its point out of a position below the upper edgeof the ventral guides into the vicinity of the lower edges of the dorsalguides, and each support is also movable with at least its point out ofa position in the region of the ventral guides into the vicinity of theupper edges thereof. Thus the fillets are subjected to the scrapingforces as a result of the connection to the skeleton in the elongatestate which is still preserved after application of the ventral anddorsal filleting cuts and extends as far as the root of the tail, whichleads to a much smoother cut surface and correspondingly improved yield.Also, as a result of complete release of the fillets not taking placeuntil after the scraping process by means of the separating cuts, thefillets can be deposited in the correct position for automatic furtherprocessing.

[0005] This known machine works largely satisfactorily for differentfish species such as rosefish, tuna and fish to be allocated to thesalmon family with, unlike the Gadidae such as pollock, cod, etc., theupper wall of the ventral cavity passing directly towards the anus. Itwas therefore attempted to use and adapt such apparatuses and methodsfor other fish species too, particularly tilapia, a farmed and/orbreeding fish with a body shape and basic bone structure similar to therosefish. However, this did not lead to satisfactory filleting results,because on the one hand with the tilapia species there are qualitativelyimportant deviations from the “normal” bone structure and the usualstructure of the ventral cavity to an uncommonly high degree in total,so that a universal application of the known machine referred to thisfish is not possible. Thus the tilapia exhibits markedly strong, curvedflank bones which do not allow “smoothing” by the known scraping tool orallow it only to an extremely limited extent, because this toolessentially forms with the (vertical) conveying plane an angle of 90°,that is, stretches the ribs in the two tool portions practically over180°. Hence there are losses of flesh. Further, with this fish speciesthe rib or flank bones are attached relatively loosely to the main body,which with the traditional peeling or scraping operation or theapparatuses used for this would easily result in these bones being tornoff from the main bodylbone structure and consequently remaining in thefillet and so result in a lower-quality product. Also in the ventralcavity region below the flank bones on either side there is an innerprotuberance essentially consisting of fatty tissue. Between these twoprotuberances extends a corium-like connection for division orseparation between ventral cavity and swim bladder. In other words,unlike the above-mentioned ordinary fish which have a two-part swimbladder in the upper region of the ventral cavity on both sides of thespine/vertebral column, the tilapia has a one-part, very large swimbladder which poses considerable problems for processing on traditionalmachines.

[0006] It is therefore the main aim of the invention to provide a methodand an apparatus with which, avoiding the drawbacks described for theknown measures, processing especially of fish of the tilapia species ispossible.

[0007] It is another aim of the invention to enable the production ofclean fillets with minimal use of personnel with a high throughput. Thisis to be effected with maximum possible yield.

[0008] This object is achieved in the method of the kind describedhereinbefore by the fact that before peeling separation in the region ofthe ventral cavity the ventral lobes are trimmed by separation of theends of their ventral lobe portions projecting beyond the ribs and thenpeeling separation is completed by scraping or peeling cuts adapted tothe rib contour and made with at least two degrees of freedom.

[0009] In the apparatus, to achieve the object it is provided that thescraping tool/peeling blades are both pivotable with lateral springyielding about an axis running essentially perpendicularly to theconveying plane and pivotable away from the conveying plane againstspring force about a hinge axis running essentially in the direction ofthe scraping or peeling edges and optionally in front of the scrapingtool or in the region thereof is arranged a trimming device for trimmingthe ventral lobes in the region of the ventral cavity by at leastpartial separation of the ends of their ventral lobe portions projectingbeyond the ribs, from the fillets covered with the skin on the outside.

[0010] In this way on the one hand by means of trimming the condition ofbeing able to detach the fillets cleanly from the bone structure byflank scraping in the tilapia in general is fulfilled. With this fishspecies, apart from the above-mentioned fatty protruberances located onthe inside of the ventral cavity and mounting between them theleather-like membrane partition from the swim bladder, the end of therib bones is connected to the outer skin, so that unclean edges wouldarise when scraping in this region. Hence there is removal of theseventral lobe portions which moreover become thicker again from theabove-mentioned connecting point downwards, i.e. towards the end of theventral cavity, and have an extremely high fat content, so that they arenot considered for a high-quality saleable product, but can be subjectedto a press sieving operation for example for subsequent fish mealrecovery.

[0011] Trimming can be done before or after separation of the filletflesh. Hence there are optionally various possibilities: on the one handthe ventral lobes can be trimmed and only then is the fish supplied tothe scraping tool; but on the other hand any desired trimming, whichthen makes subsequent manual processing e.g. with respect to the piecesof skin superfluous, can also be performed concurrently with orfollowing separation. In other words, superimposed processing orprocessing in reverse to the working sequence described above then takesplace.

[0012] In subsequent trimming outside machine processing, traditionallyas a rule the ventral lobes below the flank bones and/or skin attachedthereto must be cut off by hand. Such labour-intensive operations canthus be saved according to the invention. Due to conduction of thepeeling separation operation or peeling cuts according to the inventionwith two degrees of freedom and the lateral yieldingcapacity/pivotability of the peeling blades both vertically and awayfrom the conveying plane, on the other hand the peeling cut is performedwithout disturbance by the protuberances while removing the latter fromthe fillet, that is, the through gap between blade and cutting supportcan be enlarged at the moment of traversing of this protuberance,without interrupting the continuity of the peeling or scrapingoperation. Also, due to the double lateral yielding capacity it isensured that the peeling operation can be accomplished along the veryrigid rib bones without pressing them flat as in conventional flankscraping, in a gentle manner in relation to the very loose attachment ofthe rib or flank bones to the main fish body. Hence there is no fear ofthe bones tearing off here and partially remaining in the fillet.Moreover the high flexibility of the scraping tool means generallyimproved capacity for use of the machine because easy, preciseadaptation of the tool to the bone structure is enabled.

[0013] In a preferred development of the method it is provided thattrimming is effected after lifting the ventral lobes under the cuttingsupport by separation of the inner ventral skin as far as the end of theribs at their point of connection to the outer skin. Hence cleanseparation of the unwanted ventral lobe portions is achieved withprecision by guiding along the end of the rib or flank bones, i.e. atthe point at which the outer skin is connected to them, wherein thetrimming blades cut off the inner ventral skin from below towards thecutting support to exactly the end of the flank bones. For theapparatus, to attain this partial aim it is provided that the trimmingdevice includes a pair of circular trimming blades and a cutting supportallocated to each of them, so that the required precise trimming cut canbe performed in a structurally simple manner.

[0014] However, as the tilapia has a tough to extremely resistant,leather-like skin, difficulties in making cuts frequently arise whentrimming before peeling separation, by the fact that the skin is notcompletely cut through or not cut through at all. Then the followinglower ventral lobe portions jam in the separating gap, and in the endthe machine clogs. To counter this problem, it is further proposed bythe invention to perform trimming after peeling separation. For thispurpose the trimming device for trimming the ventral lobes canpreferably be arranged in the region of the scraping tool, in such a waythat the trimming cut is made from the inside of the fish through theventral skin at the end of the ribs up to the outer skin or into it. Asa result the ventral lobe portions then remain directly connected to thefillet, namely by the outer skin. Final separation can be done forexample in a subsequent skinning operation. Additional, if necessarymanual subsequent processing/trimming is not required in this caseeither.

[0015] To keep the stress on the relatively loose flank or rib boneconnection to the main body as low as possible, according to anotherdevelopment concept of the invention peeling is to be effected at anangle of ≦10° to the perpendicular. With respect to the apparatus, forthis purpose in an advantageous development of the invention the peelingblades can be designed as scraping blades arranged in pairs on bothsides of the conveying plane with a scraping angle of ≦10° to theconveying plane and their cutting supports at least in the input regioncan be provided with a slender, slightly thickened upper edge, whereinhere the cutting edges of the scraping blades project beyond thesupports. In this way allowance is made for the relatively firm andhighly curved structure of the flank bones. In connection with thelateral yielding capacity described for peeling blades and support thereis a clean flank cut, wherein in the rear region of the cutting supportthe cutting edge of the scraping blade is covered, that is, for approx.4 mm the cutting edge plunges away behind the support. This effect canbe further improved by optionally providing inner or lower chamfers onthe scraping or peeling blade. This particularly aids the fact that thepeeling operation adapts satisfactorily to the contour of the bones,that is, their curvature in the ventral cavity region, and the scrapingblade slides over them without being dragged into the bone structure.

[0016] A further peculiarity of fish of the species tilapia lies in thatin the anal region and practically as the rear end of the ventral cavitythey have a very strong anal bone which, when using normal saddles withconvexly curved front edge and when uniformly fitting holding spikesalong the saddle upper edge, usually arranged laterally in pairs, makesit impossible to saddle such fish reliably and definitely with respectto their position. With a conventional design of the front edge of thesaddle, the fish would be pushed to one side by the stiff anal bone.Furthermore these fish have, seen from the anal opening in the directionof the head, a thicker main bone which also makes it impossible tosaddle the fish on a regular spike assembly along the upper edges of thesaddle and to hold them effectively by the spikes. To overcome theseproblems the fish saddles of the conveyor, when they are provided with aplurality of transport spikes which ensure reliable seating of theventral cavity and at least partially penetrate the fish structure, areto be designed in such a way that from the front saddle end there areprovided initially two to three transport spikes which are followed by agap roughly corresponding to a spike division step and then, followingon behind, additional spikes. Hence it is possible for the thicker mainbone to be received on the upper edge of the saddle in this gap andmoreover for the spikes of the upper edge of the saddle to continue, asknown, to engage in the upper regions of the fish on or laterally of themain bone, in order to hold the fish fast. Furthermore, to prevent therigid anal bone from being pushed aside, the saddles can in each case bedesigned with a slightly concave projection which ultimately receivesthis anal bone in it and so centres it rather than pushing it away tothe side. If necessary this projection can be designed with a sharpfront or upper edge, which facilitates penetration of the leather-likeboundary membrane of the swim bladder and passing through it, so that ingeneral the difficulties associated with this fish species due to itsstructural peculiarities when saddling the fish can be significantlyreduced for the operating personnel.

[0017] Since both the dorsal fins and the ventral fins are relativelyhard in the tilapia and cause difficulties regarding satisfactoryinsertion in case of ordinary, split dorsal and ventral inlet guides ofscraping devices, which may lead to lateral yielding of the fish bodyand hence unusable cutting results, in a further development of theinvention it is provided that the dorsal inlet guide can be provided asa closed angle profile, while the ventral inlet guides for introducingthe ventral region of the fish into the filleting blades on the ventralside can be arranged as a double-mounted ventral inlet guide which islaterally yielding in two degrees of freedom.

[0018] Owing to the above-mentioned hard, thick dorsal fin, with thefish species tilapia there can also be losses of yield in the dorsalregion if the dorsal blades are provided only slightly at an angleaccording to the prior-art apparatuses, forming between them an angle ofup to 1.5°, i.e. 0.75° to the perpendicular, as is usual nowadays. Tocounter such draw-backs and achieve a better cutting yield, in anadvantageous development the invention proposes that, instead, thedorsal blades arranged in pairs form between them an angle ofapproximately 2 to 6°, preferably one of essentially 4°. Due to thegreater tilt, the cut is made under the dorsal fin so that an optimumflesh yield can be obtained in this region.

[0019] Further advantages and embodiments or possible designs of theinvention are apparent from the description below of the practicalexamples shown in the schematic drawings. They show:

[0020]FIG. 1 details of the fish, namely

[0021]FIG. 1A a fish body to be classed in the species tilapia, as itarrives for processing,

[0022]FIG. 1B a cross-section through the fish body along the sectionB-B indicated,

[0023]FIG. 1C the skeleton of the fish after processing of the fish bodyof FIG. 1A has taken place,

[0024]FIG. 1D the end product (fillet) with ventral lobe portion cut offby trimming;

[0025]FIG. 2 an axonometric view of the parts relevant to the-inventionof a filleting machine suitable for tilapia;

[0026]FIG. 3A a sectional view of the fish when mounted with its ventralcavity on a transport saddle approximately at the level of line III-IIIof FIG. 2,

[0027]FIG. 3B a top view of the transport saddle of FIG. 3A in astructural design according to the invention;

[0028]FIG. 4A in a side view, the inlet guide region of the fishapproximately in a position relative to the filleting tools indicated byline IV-IV in FIG. 2,

[0029]FIG. 4B a cross-section through the inlet guide of FIG. 4A withthe fish inserted here, seen in the direction of arrow B in FIG. 4A;

[0030]FIG. 5 a cross-section, showing the dorsal cut at the level of thesection plane V;

[0031]FIG. 6A a cross-section through the fish when performing thetrimming cut approximately in the section plane VI-VI;

[0032]FIG. 6B a top view of the trimming tool with cutting limit andblade cover;

[0033]FIG. 7 a cross-section through the fish at the level of thesection plane VII-VII of FIG. 2 at the level of the peeling or scrapingdevice; and

[0034]FIG. 8 a side view of a further embodiment of the assembly ofscraping tool and trimming device.

[0035] The fish intended for processing is in the form of a fish body 1which has been beheaded, slaughtered and eviscerated and is open in theventral cavity, as can be seen in FIGS. 1A and B. This is the body of afish of the species tilapia with essentially the following properties:these fish have a relatively thick main bone 110, generally alsoreferred to as the spine, from which, as can be seen in particular inFIG. 1C, a view of the skeleton or bone structure 11, dorsal bones 113extend upwardly over the whole length of the fish and ventral bones 114extend downwardly in the region in front of the caudal fin 15, while inthe region of the ventral cavity 1curved around the latter, alsostarting from the spine 110, the flank or rib bones 111 extend. At theend of the ventral cavity, running from the spine 1to the anus, the fishof the tilapia species have a relatively compact and rigid anal bone 112which extends towards the beginning of the ventral fins 14. Theseventral fins are also, i.e. like the dorsal fins, markedly stiff andthick. Within the ventral cavity are located on either side, curving upfrom the insides of the ventral lobes, inner protuberances 123 whichinclude fatty tissue and between which extends a dividing membrane 122of leather-like character, shown in dot and dash lines here. Thismembrane 122 divides the ventral cavity into the actual lower ventralcavity region 1in which are located the digestive and other vital organsof the fish, and into an upper region which is occupied by a swimbladder 121 in one part in this species. At the beginning of this swimbladder on the head side the spine 1is provided with a thicker main boneportion 115 which, as is shown later, poses problems during normalsaddling of the fish.

[0036] As can be seen from FIG. 1B, the flank bones 111 which are notshown in detail here extend as far as a location 1111 which is to bereferred to as the rib end and at which the outer skin of the fish ispractically joined to the rib ends. This location is, as can be seen,relatively thin. The ventral lobe widens again downwards, as can also beseen from FIG. 1B. As a result of this “predetermined break point” 1111,tearing off of the ventral lobe end portions 161 would be caused in thisregion during normal scraping filleting, also due to the relativelythick outer skin, which would lead to an aesthetically unattractiveproduct.

[0037] The apparatus shown in FIG. 2 serves to carry out the methodaccording to the invention in fishes of the above-mentioned species. Itincludes an endlessly rotationally driven conveyor 2 not shown in moredetail and indicated only by dot and dash lines, with fish saddles 21 onwhich the fish body 1 is firmly mounted, as is shown in FIG. 3A and willbe described in more detail below, so that it is transported by theapparatus with a stable position and with the aid of additional guidescan be processed into the primarily desired fillets 16 with a lower,secondary ventral lobe end portion 161 which is separated by trimmingand which can be further processed e.g. by known press separating, aswell as with a descending tertiary bone structure 11 with minor fleshresidues adhering to it, also to be provided by press separating.

[0038] For this purpose there are provided in each case a conventionaldorsal tool 3 as well as ventral tool 4, which each include circularblades 31 or 41 arranged in pairs. Adjoining the pair of dorsal blades31 is a dorsal guide and adjoining the pair of ventral blades 41 is aventral guide 40. With the dorsal tool 3 the dorsal bone 113 is cut freeover the whole length of the fish as far as the vicinity of the spine110, while the ventral bone 114 is cut free between caudal fin and endof the ventral cavity 120 by means of the ventral tool. Behind these twotools the above-mentioned dorsal and ventral guides or 40 then undertakeguiding of the bone structure 11.

[0039] To separate the fillets from the spine 110 in the region stillcohering between the end of the ventral cavity 120 and caudal fin 15there is provided a separating tool which cuts the fillets free from thebone structure by means of a pair of essentially parallel separatingblades 51 over the main bone 110. On the ventral side is located atrimming tool 6, including a pair of trimming blades 61 set at an angleto each other, with which the lower ventral lobe portion 161 (FIG. 1D)is separated approximately along the end of the rib bones 111 in theregion of the rib ends 1111. Both tools and 6 are provided as circularblades 51 or 61 arranged in pairs.

[0040] As the last processing tool, along the conveyor is arranged ascraping tool 7 which includes, also arranged in pairs, a peeling blade71 as well as peeling blade supports 72.

[0041] But appropriately an arrangement of the trimming device 6 in theoperating or working region of the scraping tool 7 is also possible (seein particular FIG. 8).

[0042] For details not directly concerning the invention as such,reference is made for example to the above-mentioned DE 29 46 042 B1which reflects the basic principle of a saddle-equipped conveyor withventral, dorsal, separating and scraping tools, but is not, as alreadystated, suitable for the species tilapia. There can also be seen thebasic position or basic path of the dorsal and ventral cuts in relationto the stationary strip of flesh laterally of the spine, which is cutthrough by means of the separating blades in the caudal region of thefish behind the ventral cavity.

[0043] The function of the steps and arrangements according to theinvention will now be discussed with the aid of the detailed drawings,considering the peculiarities of the fish species tilapia:

[0044] In FIGS. 3A and B is shown the saddle construction required witha view to the above-mentioned thicker region 1 of the main bone. Inorder to be able to convey the fish through the machine tail first, asis required with the method and apparatus assembly according to theinvention, after beheading, slaughtering and making the lower openingcut in the ventral cavity it is mounted head first on an ordinary saddle21 which is for example also known from DE 29 46 042 B1 and which isprovided with a row of transport spikes 22 along its lateral upperedges. These transport spikes are inclined in the opposite direction tothe direction of mounting the fish and hence in the direction ofsubsequent transport thereof, indicated by the arrow 200. Whereas withconventional saddles these rows of spikes on both sides are arrangedcontinuously, with the invention there is an arrangement whereby, seenfrom the front saddle end 24, first there are two or three spikes andthen a gap 23 which receives the thicker main bone portion 115, as canbe seen from FIG. 3A, while subsequently additional transport spikes 22follow. The thicker region 1can be embedded in this gap 23, while thefront transport spikes enter the fish body around the vertebral columnand fix it. The subsequent spikes then become operative, depending onthe length of the fish body 1.

[0045] In order that the very rigid anal bone 112, which is also shownin FIG. 3A, cannot result in the fish being pushed away laterally duringthe required powerful pushing, which would lead to unsatisfactorycutting results and a lower-quality product, the projection 25 of thesaddle end 24 is constructed concavely. It can thus receive this analbone in it or center the fish body 1 by this means.

[0046] As can be seen, the sharp teeth 22 inclined in the oppositedirection to the direction of mounting the fish in conjunction with asharpened front edge 26 of the saddle lead to the separating membrane122, which divides the ventral cavity and demarcates the swim bladder121, being destroyed in such a way that it no longer forms an obstacleto further processing.

[0047]FIGS. 4A and B show the inlet guide region approximately at thelevel of line IV-IV of FIG. 2. For the purpose of functional control ofthe hard, very resistant dorsal fins 13 on the one hand and of theequally compact ventral fins 14 a dorsal inlet guide 301 and ventralinlet guide 401 are each provided. The dorsal inlet guide 301 is, as canbetter be seen from FIG. 4B, constructed as an angle profile. Theventral inlet guide 401, which undertakes insertion of the ventral finon the tail side, is capable of lateral yielding in two degrees offreedom, namely on the one hand vertically displaceable about the axis402 extending perpendicularly to the blade plane of FIG. 4A as well ason the other hand with its guide plates 403 which are provided spacedapart on both sides of the path of conveying, yielding laterallyperpendicularly to the blade plane and hence to the conveying plane. Theconveying plane is shown for order's sake in FIG. 4B, which moreovershows the saddle 21 inside the fish, because this section IV-IV is inthe ventral cavity region.

[0048]FIG. 5 shows a cross-section through the fish at the level of thedorsal tool 3 or the dorsal blades 31, this section being shown in FIG.2 by the dot and dash line V. The two dorsal blades 31 are set at anangle of 4° to each other so that, as can be seen, they cut under thethick dorsal fin 13 and consequently leave optimum flesh on the fillet16 by cutting close to the vertebral column 110.

[0049] The section through the fish according to FIG. 6A, made along theline VI-VI of FIG. 2, shows trimming of the ventral lobes 161 by meansof the trimming tool 6 in the form of a pair of trimming blades 61. Insection, a trimming cut support 62 shown in the top view is omittedhere. It can be seen that the trimming blades 61 separate the lowerventral lobe ends 162 in the lower portion of the ventral lobes 161where the flank or rib bones 111 end and practically make a connectionwith the outer skin of the fish, wherein the cutting supports 62cooperate with the blade edges from the inside, that is, from theventral cavity 120. A blade cover 63 ensures that at the end of thetrimming cut the fillet is lifted over the trimming blades 61, so thatthe latter cannot cut into the fillet and no valuable fillet flesh islost.

[0050]FIG. 7 shows in detail the scraping tool 7 in a sectionapproximately along line VII-VII. Guided by dorsal guides from above toengage the spine and by means of the saddle 21 from below to engage thespine 110, the fish cut free in the fillets from the ventralbone/ventral spokes as well as from the dorsal bone/dorsal spokes andaround the spine moves into the region of the tips of the peeling blades71 which peel the fillet flesh free from above, beginning at thevertebral processes of the vertebral column 110, on account of theirdiverging construction—as already described in DE 29 46 042 B1—along theupper edges of the flank bones or ribs 111. This takes place incooperation with the peeling blade supports 72 by the fact that the ribsare moved through the gap between the peeling edges 711 of the peelingblades 71 and the upper edges of the peeling blade supports 72, whichgap is variable in width against spring force, depending on thethickness of the bones. To ensure precise lifting over the protuberances123, which are not shown here for reasons of simplification, and soprevent portions of the fillets being somehow cut into in this region,the peeling blades 71 like the peeling blade supports 72 are mounted soas to be laterally pivotable in addition to their (usual) verticaldisplacement capacity. For vertical pivotability the peeling blades 71are vertically pivotable about pivot axes 712 which run essentiallyperpendicularly to the conveying plane and are slightly at an anglehere, while the cutting supports 72 are mounted to be verticallydisplaceable about corresponding support pivot axes 722. This verticalpivotability is effected against the force of corresponding springs, ofwhich those for the peeling blades 71 are omitted here, while for thesupports 72 springs 72ensure the required support pressure. The lateralpivotability, that is, lateral yielding of the peeling blades 71 andsupports 72, is provided by mounting these tool portions on hinge axes713 or 723, wherein this too is guaranteed with lateral spring yieldingby means of corresponding compression springs 71or 7230.

[0051] As an advantageous variant from the above-described procedure oftrimming the ventral lobes 161 before subsequent separation of thefillets with corresponding arrangement of the trimming device 6 in frontof the scraping tool 7, FIG. 8 shows an arrangement particularlysuitable for tilapia fish with extremely tough skin, in which thetrimming device 6 is mounted directly within the operating or workingregion of the scraping tool 7. With such an arrangement, the fish cutfree in the fillets from the ventral bone/ventral spokes as well as fromthe dorsal bone/dorsal spokes and around the spine first moves into theregion of the tips of the peeling blades 71. Actual scraping orseparation takes place in cooperation with the peeling blade supports72. The fillet flesh is therefore peeled free along the upper edges ofthe flank bones or ribs 111. Only after peeling free the fillet, atleast up to the cut-open point of the trimming cut, are the ventrallobes 161 trimmed so that the initial cut of peeling separation isbefore the initial cut for trimming in time. Due to the fact that thefish first moves into the region of the scraping tool 7, the ribs arepeeled free from the fillets until the initial cut of the trimming tool,whereupon only then does trimming take place, this being in such a waythat the trimming blade 6 performs a separating cut from below as far asthe outer skin. An additional cutting support is not necessary here aslong as the trimming blade, as can be seen, is located in the region ofthe scraping tool 7 which ensures the necessary counterpressure. Furtherprocessing takes place in the same manner already described above, butwith the difference that the ventral lobe portions, joined to thefillets by the skin, are entrained with them until e.g. a subsequentskinning operation ensures final separation.

[0052] To achieve easy changing in position of the trimming tool, thatis, to be able to adapt the apparatus in general to quickly varying fishsizes, it is easy either to provide several exchange positions formounting the trimming device on the machine or to mount the trimmingdevice on a bearing rail or the like on which it is easily andinfinitely variably slidable and can be fixed. In this case naturallyallowance can also be made for different angles of inclination for thetrimming tool which, as can be seen in the drawings, should be mountedessentially at an angle to the (imaginary) conveying plane in FIG. 6 forcutting from the outside, whereas according to FIG. 8 it can lie withits blade plane practically parallel to this conveying plane for cuttingfrom the inside.

[0053] To facilitate the peeling or scraping operation with adaptationto the harder surfaces of the bones without risk of cutting into them,as is known for example from chamfer-free razor blades, the scrapingblades 71 are provided at their inner or lower edge regions facingtowards the bones with inner or lower chamfers, which however are notshown in more detail here.

[0054] Further details of the arrangement according to the invention,which is however shown only by way of example, can be dispensed withbecause its principle of operation can be seen from the drawings. Itshould only be pointed out that for design reasons e.g. the peeling cutsupports 72 are constructed in two parts and the actual support 72 isseated on a support 724, so that the latter is subjected to the springpressure of the compression spring 7220 and so the actual support 72 isnot impeded in its operation by additional ventral portions, i.e. enoughspace is available for peeling or scraping the fish. Also the pivotshaft 712 can be mounted fixed to the machine on a bearing block; henceit does not absolutely have to be seated on the dorsal guide 30, as donehere for reasons of appropriateness.

1. Method for filleting fish which have been beheaded, slaughtered andhad their ventral cavity opened, in particular for the large-scaleprocessing of certain farmed and/or breeding fish such as tilapia,wherein the fillets are detached from the bone structure (11) by meansof a) dorsal cuts made in the dorsal region as far as the vertebralcolumn (110) and exposing the dorsal spokes (113), b) ventral cuts madeon the ventral side in the caudal region (15) as far as the vertebralcolumn and exposing the ventral spokes (114), c) separating cuts madeover the vertebral column and connecting the dorsal and ventral cuts andd) peeling separation which under laterally yielding counterpressure iseffected from the vertebral column along the ribs (111) surrounding theventral cavity (120), characterised in that e) before peeling separationin the region of the ventral cavity the ventral lobes (161) are trimmedby separation of the ends of their ventral lobe portions (162)projecting beyond the ribs and f) then peeling separation is completedby peeling cuts adapted to the rib contour (111) and made with at leasttwo degrees of freedom.
 2. Method according to claim 1, characterised inthat trimming is effected after lifting the ventral lobes under thecutting support by separation of the inner ventral skin as far as theend of the ribs at their point of connection to the outer skin. 3.Method according to claim 1 or 2, characterised in that peeling iseffected at an angle of ≦10° to the perpendicular.
 4. Apparatus forfilleting fish which have been beheaded, slaughtered and had theirventral cavity opened, in particular for the large-scale processing ofcertain farmed and/or breeding fish such as tilapia, including a) dorsalblades (31) for exposing the dorsal spokes (113) up to the vertebralcolumn (110); b) ventral blades (41) for exposing the ventral spokes(114) in the caudal region (15) up to the vertebral column; c)separating blades (51) for separating the fillets in the caudal regionfrom the vertebral column, cutting through the ridge left by ventral anddorsal blades around the vertebral column; d) a scraping tool (7)including peeling blades (71) and peeling blade supports (72) forpeeling separation of the fillets from the ribs (111) surrounding theventral cavity (120) under laterally yielding counterpressure from thevertebral column; e) an endless conveyor (2) for transport of the fishtail first and past the tools according to a) to d) arranged on bothsides of an imaginary conveying plane (20) and also f) a number of fishsaddles (21) arranged on the conveyor for reliably holding the fish intheir ventral cavity for the purpose of transport and processing withthe tools, characterised in that g) the scraping tool (7) is bothpivotable with lateral spring yielding about an axis (712) runningessentially perpendicularly to the conveying plane (20) and pivotableaway from the conveying plane against spring force about a hinge axis(713) running essentially in the direction of the peeling edges (711);and h) optionally in front of the scraping tool (7) or in the regionthereof is arranged a trimming device (6) for trimming the ventral lobes(161) in the region of the ventral cavity (120) by separation of theirventral lobe portions (162) projecting beyond the ribs.
 5. Apparatusaccording to claim 4, characterised in that the trimming device (6)includes a pair of circular trimming blades (61).
 6. Apparatus accordingto claim 5, characterised in that the trimming device (6) additionallyincludes a cutting support (62) allocated to each of the circulartrimming blades (61).
 7. Apparatus according to either of claims 4 or 6,characterised in that the peeling blades (71) are designed as scrapingblades arranged in pairs on both sides of the conveying plane with ascraping angle of ≦10° to the conveying plane (20) and their cuttingsupports. (72) at least in the input region are provided with a slender,slightly thickened upper edge, wherein here the cutting edges of thescraping blades project beyond the supports.
 8. Apparatus according toclaim 7, characterised in that the peeling blades (71) are provided withan inner or lower chamfer.
 9. Apparatus according to any of claims 4 to8, in which the fish saddles (21) of the conveyor (2) are provided witha plurality of transport spikes (22) which ensure reliable seating ofthe ventral cavity and at least partially penetrate the fish structure,characterised in that from the front saddle end (24) there are providedinitially two to three transport spikes (22) which are followed by a gap(23) roughly corresponding to a spike division step and then, followingon behind, additional spikes (21).
 10. Apparatus according to any ofclaims 4 to 9, characterised in that the saddles (21) are in each casedesigned with a slightly concave projection (25), if occasion ariseswith a sharp front edge (26).
 11. Apparatus according to any of claims 4to 10, including at least one dorsal inlet guide (301) for guiding thedorsal fin (13) in sliding relationship in the fish input region,characterised in that the dorsal inlet guide is provided as a closedangle profile.
 12. Apparatus according to any of claims 4 to 11,including ventral inlet guides for introducing the ventral region of thefish (1) into the filleting blades (41) on the ventral side,characterised in that the ventral inlet guide (401) is double-mountedand designed for lateral yielding in two degrees of freedom. 13.Apparatus according to any of claims 4 to 12, characterised in that thedorsal blades (31) are arranged in pairs and form between them an angleof 2 to
 60. 14. Apparatus according to claim 13, characterised in thatthe dorsal blades (31) form between them an angle of essentially 4°.